Reconfigurable single and multi-sector cell site system

ABSTRACT

A telecommunications system is provided that is controllably operable as a sectorized antenna system and as an omnidirectional antenna system without requiring hardware reconfiguration. The telecommunications system includes a phase correlation measurement unit that can be between a sectorized antenna sub-system and a remotely located RF source site. The phase correlation measurement unit can be coupled to the RF source site over at least one feed line. The phase correlation measurement unit can output signals for controlling a phase shifter at the RF source site for phase shifting downlink signals and for causing operation of the sectorized antenna sub-system as an omnidirectional antenna sub-system. In a sectorized operation mode, the phase correlation measurement unit and the phase shifter can be inactivated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/439,938, filed Apr. 30, 2015, and titled “Reconfigurable Single andMulti-Sector Cell Site System,” which is a U.S. national phase under 35U.S.C. § 371 of International Patent Application No. PCT/IB2013/060415,filed Nov. 26, 2013, and titled “Reconfigurable Single and Multi-SectorCell Site System,” which claims priority to U.S. Provisional ApplicationSer. No. 61/730,580 filed Nov. 28, 2012 and titled “Pseudo-OmniSite-Configuration,” the entire contents of each of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to telecommunications and, moreparticularly (although not necessarily exclusively), to cell sitesystems that are reconfigurable between omnidirectional and sectorizedoperation.

BACKGROUND

When a new cell site for wireless services (i.e., mobile communication)is established, the new cell site may be the first wireless coverage tobe provided for the coverage area. When demand for more capacityincreases at a later time and beyond the capabilities of the initialinstallation, the cell site infrastructure is often physically changedto provide the needed coverage capacity. Physical changes to the cellsite infrastructure can include establishing smaller cells (i.e., morecell sites) or splitting a coverage cell into multiple sectors.Splitting a coverage cell into multiple sectors can involve lessinfrastructural changes than establishing multiple smaller cells, but itcan still involve changing much of the initially installed hardware,e.g., antennas, feeding lines, feeding hardware, etc.

When an initial cell site with an omnidirectional coverage pattern(i.e., single sector) is changed to a multi-sector site for capacity,multiple items in the installation may need to be modified atsignificant cost. For example, an omnidirectional antenna may need to bereplaced by a multi-sector antenna (e.g., a three-sector antenna), asingle coaxial feeder line may need to be upgraded to a multi-coaxialfeeder line, and a full power feeding amplifier may need to be replacedwith multiple feeding amplifiers (e.g., at one-third of full power eachin the case of three sectors).

Mechanisms and systems are needed to more efficiently transform a cellsite for providing higher capacity coverage for an area.

SUMMARY

In one aspect, a telecommunications system includes a phase correlationmeasurement unit. The phase correlation measurement unit can be betweena sectorized antenna sub-system and a remotely located radio frequency(RF) source site. The phase correlation measurement unit can be coupledto the RF source site over at least one feed line. The phase correlationmeasurement unit can be configured for outputting signals forcontrolling a phase shifter at the RF source site for phase shiftingdownlink signals and for causing operation of the sectorized antennasub-system as an omnidirectional antenna sub-system.

In another aspect, a method is provided that includes determining arectified voltage signal of a combined signal formed from at least twodownlink signals at a sectorized antenna sub-system site. The methodfurther includes controlling a phase shifter at an RF source site forphase shifting downlink signals based on a measured voltage of therectified voltage signal. The method further includes operating thesectorized antenna sub-system site as an omnidirectional antennasub-system using at least two phase-aligned downlink signals.

In another aspect, a telecommunications system includes a phase shifter,antennas, and a phase correlation measurement unit. The phase shifter ispositionable at a radio frequency (RF) source site. The antennas arepositionable at a sectorized antenna sub-system site communicativelycoupled to RF sources at the RF source site. The phase correlationmeasurement unit is positionable at the sectorized antenna sub-systemsite. The phase correlation measurement unit is configured foroutputting signals for controlling the phase shifter for phase shiftingsystem signals and for causing operation of the sectorized antennasub-system site as an omnidirectional antenna sub-system. Thetelecommunications system is switchable between operating in anomnidirectional operation mode and a multiple sector operation mode inresponse to a control signal.

The details of one or more aspects and examples are set forth in theaccompanying drawings and the description below. Other features andaspects will become apparent from the description, the drawings, and theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a multiple sector telecommunications systemoperable as an omnidirectional antenna system according to one example.

FIG. 2 is a schematic of a multiple sector telecommunications systemwith a phase correlation measurement unit and phase shifters accordingto one example.

FIG. 3 is a schematic of a multiple sector telecommunications systemwith a phase correlation measurement unit and phase shifters accordingto another example.

FIG. 4 is a schematic of a multiple sector telecommunications systemwith a phase correlation measurement unit, phase shifters, and switchesaccording to another example.

FIG. 5 is a schematic of a phase correlation measurement unit and phaseshifters according to one example.

FIG. 6 is a schematic of a phase correlation measurement unit and phaseshifters according to another example.

FIG. 7 is a schematic of a phase correlation measurement unit and phaseshifters according to another example.

FIG. 8 is a side view of a module for a phase correlation measurementunit according to one example.

FIG. 9 is a schematic top view of a phase correlation measurement unitwith representations of the boards on which components can be positionedaccording to one example.

DETAILED DESCRIPTION

Certain aspects and examples of the present disclosure are directed toestablishing a cell site for initially operating as a single-sector cellsite, but that is easily re-configurable to a multi-sector cell site ata later time without requiring replacement or upgrading of hardware. Thecell site may also be re-configurable back to a single-sector cell site.Reconfiguration of the cell site can be controlled using commands from asoftware application rather that necessitating hardware changes.

A cell site system according to some aspects can include an antennasub-system with antennas for multiple sectors. Each antenna can beassociated with a respective feed line that is coupled to a dedicatedradio frequency (RF) source, which may be located remotely from theantenna sub-system. Examples of RF sources include remote radio heads,distributed antenna system units, and base transceiver stations. In asingle-sector mode, the RF sources provide the same signal to the cellsite and the antennas radiate the same signal for providing coverage inthe coverage area by an omnidirectional coverage pattern. The signalscan be radiated in phase to each other and kept at a low group delayspread in providing omnidirectional coverage. For example, a phasedetection box can be positioned between the antenna subsystem and aremote unit that can include one or more RF sources. The phase detectionbox can be coupled to the remote unit over one or more feed lines. Thephase detection box can output control signals to phase shifters forphase shifting downlink signals and for causing the antenna subsystem tooperate as an omnidirectional antenna sub-system.

These illustrative aspects and examples are given to introduce thereader to the general subject matter discussed here and are not intendedto limit the scope of the disclosed concepts. The following sectionsdescribe various additional features and examples with reference to thedrawings in which like numerals indicate like elements, but should notbe used to limit the present disclosure.

FIG. 1 depicts an example of a multi-sector cell site that can provide asingle-sector omnidirectional coverage pattern 1. The cell site includesan antenna subsystem with sectorized antennas 2 a-c, one for each ofthree sectors. The sectorized antennas can radiate the same RF signal toprovide the omnidirectional coverage pattern 1. The sectorized antennascan receive signals through feed lines 3 a-c from RF sources representedby power amplifiers 4 a-c. The RF sources can support the same servicesignal and the signal can be radiated by the sectorized antennas 2 a-csuch that the behavior of the system is like that of a single-sectorcell site. Although three sectorized antennas 2 a-c, three feed lines 3a-c, and three power amplifiers 4 a-c (one power amplifier for each RFsource) are shown by example, any number of each can be used.

The radiated signals can be phase matched to reduce or eliminate fadingeffects between the signals radiated by the sectorized antennas 2 a-c.Phase matching can include keeping phase differences between theradiated signals to a minimum. A phase difference of more than thirtydegrees, for example, can influence (e.g., through deformation of thecoverage-pattern) a homogenous coverage. For example, the RF sources orpower amplifiers 4 a-c can have different phaseal behavior and the feedlines 3 a-c can have different phaseal behavior such that keeping afeeding service signal (e.g., service signal 1 a) phase matching may notbe sufficient. Rather, the whole signal path may need to be analyzed andcontrolled. The phase correlation between the signals can be measured atthe antennas 2 a-c and a phase correlation can be adjusted according tothe measurements to avoid fading effects at the pattern border of theantennas 2 a-c. The adjustment of the phase correlation can be usefulfor initial system setup and to compensate phase drifts over time andbased on temperature changes among other factors.

FIG. 2 depicts an example of a multiple sector cell site system that canprovide a single-sector omnidirectional coverage pattern 1. The systemcan include a phase correlation measurement unit 5 at the antennas 2a-c. The phase correlation measurement unit 5 can measure the phasedifference between the signals on connections at feed lines 3 a-b andthe phase difference between the signals on feed lines 3 b-c and thephase difference between the signals on feed lines 3 a, 3 c. The phasedifference information can be used to control the phase shifters 6 a-cin the signal path to adjust the phase difference to a minimum.

The phase shifters 6 a-c can be at the inputs of the power amplifiers 4a-c, or at any other point in the signal path to the antennas 2 a-c. Aphase shifter may be in every signal path or just in a subset of theused signal paths so that the neighboring sectors have an appropriatephase correlation. FIG. 3 schematically depicts an example of themultiple sector cell site system that includes three feed lines 3 a-cand two phase shifters 6 a, 6 c. An example for a configuration whereonly a subset of the signal paths have a phase shifter is a three-sectorconfiguration. It may be sufficient for the signal path for feed line 3a and the signal path for feed line 3 c only to have a phase shifter, asshown in FIG. 3, while the signal path for feed line 3 b is fixed. Inthis implementation, the signal path for feed line 3 a can be adjustedto minimize the phase difference with the signal path for feed line 3 band the signal path for feed line 3 c can be adjusted to minimize thephase difference with the signal path for feed line 3 b such that thethree signal paths can have a minimum phase difference with respect toneighboring signal paths.

The cell site system may be installed as a single sector antenna systemproviding omnidirectional coverage, but the system can be switched to amulti-sector antenna system without requiring hardware or other physicalchanges. The system can be reconfigured between a single sector antennasystem and a multi-sector antenna system according to a switchingsignal. In multi-sector operation, the phase correlation measurementunit 5 and phase shifters 6 a-c may not be operated since signals inmulti-sector operation are sufficiently de-correlated and phaseadjustment is not used. The phase correlation measurement unit 5 andphase shifters 6 a-c, even though not in operation, can be retained inplace such that hardware changes are not needed.

FIG. 4 depicts an example of the cell site system in which three signals8 a-c for different sectors can be switched to three sectors 9 a-c usingswitches 7 a-c. The three signals 8 a-c can be radiated as athree-sector configuration into different sectors 9 a-c such that thecell site system operates as a sectorized antenna system. For example,the switches 7 a-c can switch from providing service signals 1 a,single-sector signals, to providing signals 8 a-c along feed lines 3 a-cthrough the power amplifiers 4 a-c in response to a switching signalreceived from a control device communicatively coupled to the switches 7a-c. In some aspects, the switching signal can be communicated along thefeed lines 3 a-c to cause the phase correlation measurement unit 5 andphase shifters 6 a-c to cease operation. The switching signal can begenerated in a control device in response to a software applicationexecuting in the control device according to a user input orautomatically upon detection of a specified event.

Phase correlation measurements according to various embodiments can beperformed in various ways and using different types of componentconfigurations.

FIG. 5 schematically depicts an example of a phase correlationmeasurement unit 5 and phase shifters 6 a, 6 c in the cell site systemaccording to one aspect. The signals from feed lines 3 a-c can bede-coupled from the feed lines 3 a-c by RF decouplers 10 a-c. Thede-coupled signals can be combined by combiners 11 a-b. For example, ade-coupled signal from feed line 3 a can be combined with a de-coupledsignal from feed line 3 b and combined by combiner 11 a. A de-coupledsignal from feed line 3 c can be combined with the de-coupled signalfrom feed line 3 b and combined by combiner 11 b. The combined signalscan be rectified by rectified circuitry 12 a-b to form rectifiedvoltages. The direct current (DC) rectified voltage can be coupled thefeed lines 3 a, 3 c by DC on-couplers 14 a-b and communicated towardphase shifters 6 a, 6 c on feed lines 3 a, 3 c. Bias-T circuitry 15 a-bcan de-couple the rectified voltages from the feed lines 6 a, 6 c. Thephase shift controllers 16 a-b can measure the rectified voltages andcause the phase shifters 6 a, 6 c to modify or retain the phase shift ofthe signals based on the measured voltages. For example, the phase shiftcontrollers 16 a-b can cause the phase shifters 6 a, 6 c to shift thephase of the signals until the measured voltages reaches a maximum as amaximum DC voltage can indicate a best phase-matching condition. Aminimum DC voltage, in contrast, may indicate a condition in which twosignals are, or are approximately, 180° out of phase.

In some implementations, signals from feed lines 3 a and 3 b aremeasured and phase shifted until a maximum DC voltage is detected. Thensignals from feed lines 3 b and 3 c are measured and the signal for feedline 3 c is phase shifted until a maximum DC voltage is detected. Whensignals from feed lines 3 a and 3 b are in phase and signals from feedlines 3 b and 3 c are in phase, signals from feed lines 3 a and 3 c arein phase.

The rectified voltages can be sent to the phase shift controllers 16 a-bon the feed lines 3 a, 3 c to avoid additional wiring. But the rectifiedvoltages can be sent to the phase shift controllers 16 a-b through anycommunication channel.

The signals may be test signals. The test signals may be continuous wave(CW) signals, which may exclude effects of group delay differences onmeasurement accuracy. Any type of test signal can be used. In someaspects, the test signals can be modulated service signals transmittedduring normal operation of the system. The modulated service signals canbe combined and filtered using a bandpass filter to approximate thecombined signal as a CW signal in reducing effects of group delaydifferences for measurement accuracy. The service signal can beapproximated to a CW signal by the bandpass filter by the filterlimiting the bandwidth of the signal such that group delay differenceswithin the resulting bandwidth of the test signal can be close to zero,or otherwise negligible, which can be useful for measurement accuracy.The group delay differences among downlink signals may not be reduced.

The phase correlation measurement unit 5 may be a phase detection boxthat includes two boards: an RF board with high-quality factor materialand a detection board that can have lower quality than the RF board. Thephase correlation measurement unit 5 that includes the two boards canresult in the phase correlation measurement unit 5 being a small sizeand providing high isolation and low insertion loss at a lowmanufacturing cost. FIG. 8 depicts a side view of an example of a module30 for the phase correlation measurement unit 5. The module 30 includesan RF board 32, a detection board 34, and a metal plane 36 between theRF board 32 and the detection board 34 for isolating components on theRF board 32 from components on the detection board 34. FIG. 9schematically depicts a top view of the phase correlation measurementunit 5 and illustrates the boards on which components can be positioned.For example, the components (i.e., feed lines 3 a-c, RF de-couplers 10a-c, and on-couplers 14 a-b) depicted with solid lines can be on the RFboard 32 of FIG. 8 and components (i.e., combiners 11 a-b, rectifiedcircuitry 12 a-b and 180° phase shifters 20 a-b) depicted with dashedlines can be on the detection board 34 of FIG. 8. Further metal planes37 on the RF board 32 can be positioned between the feed lines 3 a and 3b and between the feed lines 3 b and 3 c, respectively, to increaseisolation between the feed lines 3 a-c.

The phase correlation measurement unit 5 can operate without requiringan external voltage supply. For example, the phase correlationmeasurement unit 5 can generate a DC voltage from the RF signals and canbe powered from energy from the RF signals. In other embodiments, thephase correlation measurement unit 5 is powered by an external voltageby using at least one of the feed lines 3 a-c for supplying the voltage.

The phase correlation measurement unit 5 can allow the phases of two ormore RF signals to be automatically adjusted and correlated by relativemeasurements. In some implementations, absolute detected voltage can beless important unless a minimum or maximum voltage is reached such thattuning expenses can be reduced (e.g., no calibrations for measurementsetup) and accuracy can be increased. When a minimum or maximum voltageis reached, the absolute detected voltage may be less important. Inother implementations, absolute phase differences are determined by thephase correlation measurement unit 5.

FIG. 6 schematically depicts an example of the phase correlationmeasurement unit 5 and phase shifters 6 a, 6 c in the cell site systemaccording to another example. The phase correlation measurement unit 5includes fixed 180° phase shifters 20 a-b—one positioned betweende-coupler 10 a and combiner 11 a, and another positioned betweende-coupler 10 c and combiner 11 b. Including fixed 180° phase shifters20 a-b can result in minimum RF and voltage levels after phasedifferences are equalized (i.e., zero degrees—the intended operationmode for a single-section system), and may result in better selectivityof voltage over phase at minimum voltages. Intermodulation products canbe minimized without additional filter elements. The DC voltage can be aminimum when two de-coupled RF signals have a zero degree phasedifference.

The use of filters (e.g., bandpass, lowpass, highpass) can allow for thegeneration of intermodulation products to be minimized, for broadband orother types of systems, that operate with correlated signals and withuncorrelated signals (i.e., multi-sector). FIG. 7 schematically depictsan example of the phase correlation measurement unit 5 and phaseshifters 6 a, 6 c in the cell site system according to another examplein which filters 22 a-b filter the combined signals prior to thecombined signals being rectified for minimizing intermodulationproducts.

In some implementations, signal processing in the phase correlationmeasurement unit 5 or in another location in the system can combine thede-coupled signals and analyze the combined signals. The analysis of thecombined signal itself or in combination with a controlledphase-shifting can produce information usable for setting the phaseshifters 6 a, 6 c to a position for maximum phase correlation.

Certain implementations can provide a phase correlation measurement unitthat is a phase detection box requiring no external voltage supply. Thephase detection box can provide a DC voltage for evaluation, which canbe easier to transport and process than RF signals, and continuoussupervision during system operation. Phase adjustment can be implementedusing a service signal such that no test signal or switching off theservice signal is necessary. Intermodulation products can be minimizedin some implementation using a 180° phase shift and additional filterscan be used in some implementations. Low insertion loss, high isolationbetween RF paths without degradation of measurement accuracy, low cost,and small size can be achieved. Phase adjustment and alignment can beperformed by relative measurements (e.g., a minimum or a maximum) suchthat expenditures for tuning can be reduced and accuracy can beincreased.

The foregoing description of the aspects, including illustratedexamples, of the invention has been presented only for the purpose ofillustration and description and is not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Numerousmodifications, adaptations, and uses thereof will be apparent to thoseskilled in the art without departing from the scope of this invention.

What is claimed is:
 1. A method, comprising: determining, by a phasecorrelation measurement unit, a rectified voltage signal of a combinedsignal formed from at least two downlink signals at a sectorized antennasub-system of a cell site; controlling a phase shifter at a radiofrequency (RF) source of the cell site for phase shifting downlinksignals based on a measured voltage of the rectified voltage signal,wherein the RF source of the cell site is located remotely from thesectorized antenna sub-system of the cell site; and operating thesectorized antenna sub-system of the cell site as an omnidirectionalantenna sub-system using at least two phase-aligned downlink signals. 2.The method of claim 1, further comprising: inactivating the phaseshifter when switching the sectorized antenna sub-system of the cellsite to a multiple sector operation mode.
 3. The method of claim 1,wherein multiple antennas of the sectorized antenna sub-system of thecell site radiate common information content into a coverage area whenoperating in a omnidirectional operation mode, wherein the multipleantennas of the sectorized antenna sub-system of the cell site radiatedifferent signals into different sectors of the coverage area whenoperating in a multiple sector operation mode.
 4. The method of claim 1,further comprising switching the sectorized antenna sub-system of thecell site from a omnidirectional operation mode to a multiple sectoroperation mode in response to a control signal without changing hardwarecomponents of the sectorized antenna sub-system of the cell site.
 5. Themethod of claim 1, further comprising: phase shifting each of a firstdownlink signal and a second downlink signal such that the measuredvoltage is a maximum voltage or a minimum voltage, without phaseshifting a third downlink signal.
 6. The method of claim 1, wherein theat least two downlink signals are continuous wave signals at a centerfrequency of passband and that exclude effects of group delaydifferences for determining the measured voltage of the combined signal.7. The method of claim 1, wherein the at least two downlink signals aremodulated service signals provided from RF sources of the cell siteduring normal system operation, the method further comprising: filteringthe combined signal using a bandpass filter to approximate the combinedsignal as a continuous wave signal in reducing group delay differencesamong the at least two downlink signals.
 8. The method of claim 1,wherein controlling the phase shifter at the RF source of the cell sitefor phase shifting downlink signals based on the measured voltageincludes: phase aligning signals along a first feed line and a secondfeed line; and phase aligning signals along the second feed line and athird feed line such that the signals along the first feed line and thethird feed line are aligned.